(1) Field of the Invention
The present invention relates to a gateway apparatus to be connected to a plurality of user terminals more particularly, to a gateway apparatus with an LAC (L2TP Access Concentrator) function to be applied to an ISP (Internet Service Provider) selection type IP network connecting a plurality of ISP networks connected to the Internet by an access network, in which a user terminal accesses the Internet via the access network and any of the ISP networks.
(2) Description of the Related Art
In nowadays where 70% or more of Internet traffic is occupied by Web access traffic, aiming at increasing the speed of Web access from user terminals and reducing traffic on a network connecting user terminals and Web servers, Web caching is being actively studied.
In the Web caching technology, a Web cache server (or Web caching server) is connected to an access network accommodating user terminals, a part of contents data provided by a Web server is stored as cache data in the Web cache server, and the contents data is distributed from the Web cache server in place of the Web server to the user terminals, thereby realizing increase in speed of an access to the Web from a user terminal and reduction in traffic on a core network to which the Web server is connected.
Conventionally, in the field of a network for accessing the Internet, each ISP has its own access points distributed in its service areas. Recently, an ISP selection type IP network is becoming promising, in which a plurality of ISP networks are connected to a regional IP network (or wide area IP network) managed by a communication carrier, gateway apparatuses as access points commonly used by the plurality of ISPs are disposed on the regional IP network, and user terminals connected to each of the access points are selectively connected to any one of the ISP networks.
In the ISP selection type IP network, a gateway apparatus called an LAC (L2TP Access Concentrator) is installed at a connection point between the regional IP network as an access network and user terminals, and a gateway apparatus called an LNS (L2TP Network Server) is installed at a connection point between the regional IP network and each of ISP networks.
A user terminal accessing the Web establishes a PPP connection between the user terminal and the LAC. The PPP connection is extended to an ISP network designated by the user through an L2TP connection established between the LAC and the LNS.
Specifically, at the time of establishing the PPP connection, when user ID and the identifier of a terminating ISP are input from the user terminal, the LAC connected to the user terminal specifies an LNS corresponding to the terminating ISP on the basis of the ISP identifier, and extends the PPP connection established between the user terminal and the LAC to the specified LNS through the L2TP connection established between the LAC and the LNS. The LNS authenticates the user ID of the terminal user and determines whether the user terminal and the ISP can be connected to each other or not.
The extension of the PPP connection according to the L2TP and the functions of the LAC and LNS are described in the IETF draft RFC2661.
In the ISP selection type IP network, in order to reduce communication cost in the access network (regional IP network or wide area IP network) connecting the LAC and each of the LNSs, the traffic between the LAC and each of the LNSs is demanded to be lessened as much as possible.
To reduce the traffic on the access network, for example, such a network configuration may be useful in which a Web cache server connected to each LNS on a conventional network is located on the LAC side so as to respond to a Web access from each of user terminals at the entrance of the access network.
In the conventional access network of the L2TP type, however, IP packets transmitted from the user terminal are transferred via a preset PPP connection to the connection end, so that a specific IP packet cannot be branched in some midpoint of the PPP connection.
In other words, the conventional gateway apparatus operative as an LAC simply relays a received PPP frame including an IP packet transmitted from the user terminal to the access network side through the PPP connection and does not have a function of processing the received packet at the IP level. Consequently, in the conventional technique, it is impossible to transfer a Web access request to the Web cache server at the entrance of the access network and respond to the access request from the Web cache server.
An object of the invention is to provide a gateway apparatus operative as an LAC capable of reducing the Web traffic in an access network of an ISP selection type IP network.
Another object of the invention is to provide a gateway apparatus operative as an LAC with the function of taking IP packets for Web traffic from a PPP connection and transferring the IP packets to a Web cache server.
To achieve the objects, the invention provides a gateway apparatus connected to an access network accommodating at least one ISP (Internet Service Provider) network connected to the Internet, and having an LAC (L2TP Access Concentrator) function of transferring a PPP (Point to Point Protocol) frame received from a user terminal to the ISP network via an L2TP (Layer 2 Tunneling Protocol) connection established on the access network, including:
a cache server interface for communicating a packet with a cache server for storing, as cache data, a part of contents data provided by a Web server connected to the Internet; and
packet transfer controller for selecting a PPP frame in which a Web contents request message is included in a payload field from a stream of PPP frames received from a user terminal, transferring the request message indicated in the PPP frame to the cache server via the cache server interface, and transferring a response message in a PPP frame format, received from the cache server via the cache server interface to the user terminal requesting the Web contents.
The invention also provides a gateway apparatus connected to an access network accommodating a plurality of ISP networks connected to the Internet and having an LAC function of transferring a PPP frame received from a user terminal to any one of the ISP networks corresponding to an ISP subscribed by the user of the user terminal via an L2TP connection established on the access network, including:
a cache server interface for communicating a packet with a cache server for storing, as cache data, a part of contents data provided by a Web server connected to the Internet; and
packet transfer controller for selecting a PPP frame in which a Web contents request message is included in a payload field from a plurality of PPP frames received from a plurality of user terminals subscribing different ISPs, transferring the request message indicated in the PPP frame to the cache server via the cache server interface, and transferring an IP packet in a PPP frame format, including a response message received from the cache server via the cache server interface to the user terminal requesting the Web contents.
In a first embodiment of the invention, the packet transfer controller identifies the PPP frame including the Web contents request message by checking the relation between a destination address of an IP header included in each of the PPP frames received from the user terminal and a specific IP address assigned to the cache server.
In another embodiment of the invention, the packet transfer controller identifies the PPP frame including the Web contents request message by checking an upper layer protocol of an IP packet included in each of the PPP frames received from the user terminal. For example, a port number in a TCP (Transmission Control Protocol) or UDP (Use Datagram Protocol) of an IP packet included in each of the PPP frames is checked, and a received PPP frame whose port number is xe2x80x9c80xe2x80x9d indicative of HTTP (Hyper Text Transfer Protocol) is determined as a PPP frame for a Web contents request message.
The other objects and features of the invention will become apparent from the following description of the embodiments of the invention.